Conventional vehicle seatbelts typically take either of two main forms. The simplest is a lap belt that is secured on either side of the passenger's waist and extends across the waist in use. The most common is a lap-sash belt that similarly has a lower waist section extending across the waist of the passenger as well as an upper torso section extending diagonally across the torso from one side of the waist to the opposite shoulder of the passenger.
In the event of a vehicle accident, the waist section of both the above seatbelt types typically applies a large force across the lower abdomen of a passenger. This can cause serious abdominal injury to the passenger and is particularly dangerous for pregnant women.